The present invention relates to a process and an apparatus for utilizing energy produced by the phase change of a liquid. Generally speaking, the liquid possesses the characteristic properties that the saturated vapor pressure of the liquid increases with the temperature increasement in the range of temperature between the freezing point of the liquid and the critical temperature thereof, while the saturated vapor pressure of the liquid decreases with the temperature decreasement thereof. The saturated vapor of the liquid condenses, when a pressure higher than the saturated vapor pressure of the liquid is added to the saturated vapor of the liquid, while the saturated vapor of the liquid is liquefied with the temperature decreasement of the liquid. The phase change either of the liquefaction of the vapor or the gasification of the liquid occurs depending on the interrelationship between the temperature change and the pressure change, the saturated vapor pressure of the liquid being the border therebetween. It is necessary to give the latent heat of gasifying the liquid in order to cause the phase change of gasifying the liquid and to remove the condensation heat from the vapor of the liquid to liquefy the vapor. The present invention relates to the process utilizing energy in which the principle mentioned above is applied, namely, the process relates to the process utilizing energy characterized by forming the circulating circuit comprising (a) the step of ascending the vapor of the liquid from the low place to the high place utilizing the pressure difference between the vapor pressure of the liquid generated when the liquid is vaporized by being heated at the low place and that generated when said ascending vapor of the liquid is cooled to be liquefied at the high place; (b) the step of cooling said ascending vapor at the high place to be liquefied and preferably, utilizing the heat energy of the ascending vapor when said vapor is liquefied; (c) the step of utilizing the potential energy of the liquid which has been liquefied at the high place and (d) the step of vaporizing the liquid after it has descended by repeated heating of the said liquid. The specific substance, for example, Fron-22 and Fron-500, which are the trademarks of fluoro-carbon polymers manufactured by Daikin Industrial Co. of Osaka, Japan, are vaporized within the vaporizer by the aid of the heat coming from the unused heat source, for example, the heat of the earth, the heat of hot springs, the atmospheric temperature, the solar heat, the heat of the sea water and/or the heat of the warm waste water of factory and power plant. The vapor of the specific substance ascends from the low place to the high place through the conduit connecting said high and low places by the pressure difference between the vapor pressure generated at the low place and that generated at the high place. The vapor pressure of the ascending vapor at the high place depends on the vapor pressure generated at the low place, the weight of the vapor which is the product of the height of the conduit and the density of the vapor, the loss of the vapor pressure caused by the inner resistance of the conduit and the depression of the temperature within the conduit. At that time, the phase state of the fluid within the conduit is the liquid state, the wet vapor state, the super-heated vapor state or the gaseous state, depending on both the temperature and pressure influences. The ascending vapor within the conduit at the high place is led to the heat exchanger or the cooling apparatus to be cooled by means of the atmospheric temperature, the water temperature, the wind temperature and the latent heat of evaporation of water, whereby said vapor is cooled and liquefied, the heat of the condensation being taken away through the heat exchanger or the cooling apparatus.
The temperature and the pressure of the liquid vapor to be liquefied are determined on the basis of the characteristic feature of said liquid, when the said liquid is selected taking in account of the sort of the heat source to be utilized, the temperature and the amount thereof, the cooling capacity of the heat exchanger, the diameter of the conduit, the height and the length thereof and the capacity of the heat insulation of the conduit. The more the pressure difference between the vapor pressure corresponding to the temperature of the condensed liquid at the high place and that of the ascending vapor coming from the low place becomes large, the more the amount of the ascending vapor increases. The liquid liquefied by removing the heat of the condensation through the heat exchanger or the cooling apparatus at the high place is gathered into the liquid storage tank positioned beneath the heat exchanger and then the potential energy of the descending liquid is utilized to the power source for driving the turbine while descending within the conduit, and finally the said liquid enters into the vaporizer using the unused heat source. The pressure of the liquid at the inlet of the vaporizer, after driving the turbine, is determined by the sum of (A) the product of (a) the difference of the height between the position of the liquid storage tank provided below the turbine and that of the inlet of the vaporizer and (b) the density of the liquid, and (B) the inner pressure of the said storage tank corresponding to the vapor pressure of the liquid within the liquid storage tank. As the pressure of the liquid at the inlet of the vaporizer is necessary to be higher than that within the vaporizer in order to feed the liquid into the vaporizer, it is important to determine the position of the liquid storage tank provided beneath the power plant. As occasion demands, the liquid liquefied may be fed under the pressure into the vaporizer to raise the liquid pressure by the aid of a pump.
The liquid suitable for use in the present invention demands the following phase change characteristics, from the efficiency standpoint:
(1) The relatively small latent heat of the vaporization of the liquid.
(2) The high vapor pressure, the low density and the low viscosity at the temperature of the vaporization.
(3) The low vapor pressure, the high liquid density and the low viscosity of the liquid at the temperature of the liquefaction.
(4) The high chemical and thermal stability of the liquid.
In case that the circulation circuit of the present invention for utilizing energy is used to transfer the heat energy from the low place to the high place, that is one of the objects of the present invention, it is suitable to use the liquid having the high latent heat of the vaporization.
Moreover, it is necessary to take the following characteristics (the capacity and the construction) of the apparatus of the present invention into consideration in order to select, with the good efficiency, the liquid having the characteristics suitable to the arrangement of the apparatus of the present invention, the heating medium and the amount of energy to be absorbed.
(1) The heat value to be absorbed and the temperature of the vapor in the vaporizer depending on the temperature and the amount of the heating medium in the heating and vaporizing apparatus.
(2) The heat value to be cooled and the temperature of the liquid liquefied depending on the mass and the temperature of the liquid in the cooling and liquefying apparatus.
(3) The difference of the height between the position of the vaporizer and that of the cooling and liquefaction apparatus, the diameter of the conduit, the root, the total length of the inclined conduit, the inner resistance and the heat insulating capacity of the conduit.
(4) The amount of energy to be utilized.
(5) Variations of the various factors and the surrounding conditions during all the year.
The liquid suitable to be used in the present invention comprises, for example, fluoronated hydrocarbon, chlorinated hydrocarbon, brominated hydrocarbon, fluorochloro hydrocarbon, fluorobromo hydrocarbon, light fraction hydrocarbon, lower alcohol, lower thioalcohol, lower alkyl ether, lower alkylthioether, alkylsulfoxide, toluene, xylene, or the mixture thereof and ammonia.
The circulation circuit of the present invention is used to transfer the potential energy from the low place to the high place, that is another object of the present invention.
To mainly utilize the potential energy, the liquid or the heated liquid is uniformly mixed with the saturated vapor or the super-heated vapor of the said liquid generated in the vaporizer positioned at the low place. The wet-vapor stream containing the mist of the liquid ascends from the low place to the high place by the vapor pressure of the ascending vapor. The ascending of the wet vapor stream containing the mist of the liquid is carried out by the pressure difference between the vapor pressure of said stream ascending from the low place and that of said stream at the liquifying temperature when it is liquified at the high place. The energy of the ascending vapor is converted to the potential energy by selecting and regulating the degree of drying of the ascending dry vapor to the optimum value by means of uniformly mixing the liquid or the heated liquid with the ascending dry vapor taking the said height and the temperature or pressure difference of the vapors therebetween into consideration thereby effectively utilizing energy of the ascending dry vapor at the low place, economizing energy required to condense the wet-vapor at high place, producing the large amount of the potential energy of the liquid and enhancing the utilizing efficiency of the energy held in the ascending vapor. Namely, in case that it is unneccessary to utilize the heat energy of the ascending vapor at the high place, as the process for effectively utilizing the heat energy and the ascending energy of the ascending vapor, the said liquid is uniformly mixed with the vapor coming from the vaporizer to make the wet-vapor thereby increasing the amount of transferring the liquid from the low place to the high place and relatively reducing the cooling energy for condensing the wet-vapor at the high place and producing the potential energy with good efficiency. According to the process as mentioned above, it makes possible to obtain the large potential energy in case that the distance between the low place and the high place is short, namely in said case, the utilization efficiency of the potential energy of the ascending vapor is greatly impvoed by using the wet vapor containing the mist of liquid instead of the dry vapor of liquid.